The present invention relates to disc drive storage devices. More particularly, the present invention relates to a head suspension assembly that provides enhanced shock protection to the head by increasing the shock threshold required to separate the head from the surface of the disc.
FIG. 1 illustrates a typical computer disc drive 20 that includes one or more discs 22 mounted on a hub 24 for rotation about a spindle shaft 25. The discs 22 are typically coated with a magnetic medium for storage of digital information in a plurality of circular, concentric data tracks. A spindle motor rotates the hub 24 and the attached discs 22 about the shaft 25 to allow a head or xe2x80x9csliderxe2x80x9d 26 carrying electromagnetic transducers to pass over each disc surface and read information from or write information to the data tracks.
The slider 26 is typically formed from a ceramic block having a specially etched air bearing surface that forms an air cushion or xe2x80x9cbearingxe2x80x9d as the disc rotates beneath the slider. The hydrodynamic lifting force provided by the air bearing surface causes the slider 26 to lift off and xe2x80x9cflyxe2x80x9d a very small distance above the surface of the disc 22 as the disc spins up to its operating speed. Although the fly height of the slider 26 is only a fraction of a micron, this thin film of air between the slider 26 and the disc 22 prevents damage to the fragile magnetic coating on the surface of the disc.
The slider 26 is preferably moved between data tracks across the surface of the disc 22 by an actuator mechanism 28 such as a rotary voice coil motor. The actuator 28 includes arms 30 (FIGS. 1 and 2) attached to each of the sliders 26 by flexible suspensions 32. Each suspension 32 essentially comprises a flat sheet metal spring that exerts a controlled preload force on the slider 26 in the vertical direction (i.e., against the surface of the disc 22 as shown in FIG. 2). The preload force supplied by the suspension 32 effectively counters the hydrodynamic force generated by the slider 26 and prevents the slider from flying too far off the surface of the disc 22. Although relatively flexible in the vertical direction, the suspension 32 is relatively stiff in the lateral direction in order to provide for precise lateral positioning of the slider 26 over the closely spaced data tracks.
The suspension 32 typically includes a relatively stiff load beam 34 (FIGS. 2 and 3) and a relatively flexible gimbal 36 (FIG. 3) for attaching the slider 26. A first or proximal end 38 (FIG. 2) of the load beam 34 is attached to the arm 30 of the rotary actuator 28, and a relatively flexible region 40 of the load beam 34 adjacent the actuator arm 30 is typically bent downward toward the surface of the disc 22 to supply the aforementioned preload force. A second or distal end 42 (FIG. 3) of the load beam 34 opposite the actuator arm 30 is attached (such as by welding or by an adhesive) to the more flexible gimbal 36 which, in turn, is fixed to the slider 26. An end of the gimbal 36 includes a cutout region defining two parallel flexure beams 44 and a cross member 45 defining an attachment pad 46. A tongue 47 of the load beam 34 typically protrudes within the cutout region of the gimbal 36 so that a dimple (not shown) on the bottom of the tongue 47 may contact a top surface 48 of the slider 26 to transfer the preload force directly to the slider 26. The attachment pad 46 of the gimbal 36 is secured to the top surface 48 of the slider, such as by an adhesive, so that the flexure beams 44 provide a resilient connection between the slider 26 and the relatively stiff load beam 34. The resilient connection provided by the gimbal 36 is important to allow the slider 26 to pitch and roll (i.e., xe2x80x9cgimbalxe2x80x9d) while following the topography of the rotating disc 22.
Although the preload supplied by the load beam 34 is effectively countered by the hydrodynamic force generated by the slider 26 during rotation of the disc 22, that same preload force typically forces the slider 26 to rest on the surface of the disc 22 once the disc stops spinning and the hydrodynamic force dissipates (e.g., when the disc drive 20 is powered down). During these periods of inactivity, and particularly during assembly, shipping and handling of the disc drive 20 before the drive is assembled within a computer, the fragile magnetic coating on the surface of the disc 22 is susceptible to damage from accidental vertical displacement of the slider 26, such as by a shock event.
Vertical displacement of the slider 26 may occur when a disc drive 20 is subjected to a shock of sufficient magnitude to cause the actuator arm 30 and the attached suspension 32 to move away from the disc surface (either on the initial shock or on a rebound from the initial shock). Although the bend region 40 in the load beam 34 and the resilient nature of the gimbal 36 tend to hold the slider 26 against the disc surface even as the actuator arm 30 moves away from the disc 22, a sufficiently large shock (e.g., a shock 200 times the acceleration of gravity or 200 xe2x80x9cGsxe2x80x9d) will typically overcome the preload force and cause the slider 26 to be pulled off the disc surface. The return impact of the slider 26 against the disc surface can cause severe damage to the thin magnetic coating on the surface of the disc. If the shock event occurs during operation of the disc drive, the damage to the disc coating may create an unusable portion or sector of the disc and a potential loss of data stored on that portion of the disc. However, most large shock events typically occur during periods of inactivity, as described above, when the slider 26 is positioned along an inner radial portion or xe2x80x9clanding regionxe2x80x9d of the disc 22 not used for data storage. Regardless of whether the impact occurs in the data region or the landing region of the disc 22, the impact typically generates debris particles that can migrate across the surface of the disc 22 and interfere with the air bearing surface of the slider 26, thereby causing damage to more vital regions of the disc 22 during disc operation and possibly leading to a disc xe2x80x9ccrash.xe2x80x9d
Previous efforts to minimize the above described xe2x80x9chead slapxe2x80x9d phenomenon have focused on reducing the mass of the suspension 32 between the bend region 40 and the head or slider 26. Due to the resiliency of the bend region 40 of the load beam 34, it is primarily the mass of the end portion of the suspension 32 distal to the bend region 40 that determines the lifting force applied to the slider 26 during a shock event. That is, if the force tending to pull the head or slider 26 off the disc surfacexe2x80x94as measured by the acceleration of the shock event (the number of Gs) multiplied by the combined mass of the slider 26 and the portion of the suspension 32 distal to the bend region 40xe2x80x94is greater than the preload force applied by the load beam 34, then the slider 26 will separate from the disc surface resulting in a xe2x80x9chead slapxe2x80x9d as described above.
Therefore, a reduction in the mass of the suspension 32 distal to the bend region 40 leads to a reduction in the force applied to the slider 26 during a shock event and thus to improved shock performance for the disc drive 20.
However, reducing the mass of the suspension 32 typically leads to further problems and design compromises. For example, the typical method for reducing the mass of the suspension 32 entails shortening the portion of the suspension between the bend region 40 and the slider 26. However, shortening the suspension tends to increase the variation in the preload force applied by the suspension since the shorter suspension can not typically accommodate variations in the bend angle of the load beam 34 at the bend region 40. In other words, longer suspensions 32 provide lower variations in the preload force resulting from manufacturing tolerances in the bend region 40, while shorter suspensions trade enhanced shock performance for higher variations in the preload force due to these same manufacturing tolerances in the bend angle at the bend region 40. Due to the requirement for careful balancing of the preload force against the hydrodynamic force created by the slider 26, any significant variation of the preload force may cause damage to the fragile surface of the disc 22.
It is with respect to these and other background considerations, limitations and problems that the present invention has evolved.
The present invention relates to a disc drive assembly having a suspension that provides enhanced shock protection to the head or xe2x80x9csliderxe2x80x9d of each disc by increasing the shock threshold required to separate the slider from the surface of the disc.
In accordance with one embodiment of the present invention, a suspension is provided for connecting a slider to an actuator arm of a disc drive. The suspension is adapted to maintain the slider substantially engaged with a disc surface positioned below the suspension. The suspension includes a load beam defining a first bend region adjacent a proximal end of the load beam and a second bend region adjacent a distal end of the load beam. The suspension also includes an overlapping member attached to a top surface of the load beam. The overlapping member has a first segment fixed to the load beam on one side of the second bend region and a second segment that extends over the second bend region to releasably engage the load beam on the other side of the second bend region when the distal end of the load beam is placed under a predetermined operating load.
In one embodiment of the present invention, the overlapping member comprises a gimbal adapted to attach the slider. The first segment of the overlapping gimbal is fixed to a distal portion of the load beam so that the second segment of the overlapping gimbal releasably engages a proximal portion of the load beam between the first and second bend regions.
In another embodiment of the present invention, the overlapping member is separate from a gimbal that is fixed to the distal end of the load beam for securing the slider. The first segment of the overlapping member is thus fixed to a proximal portion of the load beam between the first and second bend regions so that the second segment of the overlapping member releasably engages a distal portion of the load beam.
The present invention can also be implemented as a disc drive assembly having at least one disc mounted on a hub for rotation about a spindle shaft and an actuator for moving an actuator arm above the surface of the disc. A suspension connects a slider to the actuator arm to maintain the slider substantially engaged with the disc surface. The suspension includes a load beam having a proximal end attached to the actuator arm and a distal end engaging the slider. The load beam defines a first bend region adjacent the proximal end and a second bend region adjacent the distal end of the load beam. The suspension includes an overlapping member having a first segment fixed to the load beam on one side of the second bend region and a second segment that extends over the second bend region to releasably engage the load beam on the other side of the second bend region when the distal end of the load beam is placed under a predetermined operating load.
The present invention can also be implemented as a suspension for connecting a slider to an actuator arm of a disc drive. The suspension includes a load beam defining first and second bend regions, a proximal portion between the first and second bend regions, and a distal portion distal to the second bend region. The first and second bend regions are each preloaded to urge the distal portion of the load beam downward, the preload force of the first bend region being larger than the preload force of the second bend region. An overlapping member has a first segment fixed to the load beam on one side of the second bend region and a second segment extending over the second bend region to releasably engage the load beam on an opposite side of the second bend region when the distal end of the load beam is placed under a load that is greater than the preload force provided by the second bend region.
The present invention can further be implemented as a suspension assembly for supporting a slider within a disc drive. The suspension assembly includes a load beam having a distal end adapted to attach the slider and a bend region urging the distal end downward. The load beam further includes an intermediate locking hinge positioned between the bend region and the distal end for substantially isolating the distal end and the attached slider from upward movement of the load beam.
The present invention can further be implemented as a disc drive assembly having a slider engaging a surface of a disc and means for increasing a shock threshold required to separate the slider from the disc surface.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.